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How to Insulate Walls Without Removing the Drywall [7 Steps]

You can spray foam insulation into your walls through holes drilled in the drywall. This process does not require you to remove the drywall. To do this, first, you must locate the studs in your walls and mark them. Then, you must find the location of any wires and plumbing inside your walls. Once you know where the studs and other in-wall elements are, drill a hole between each set of studs, 8 inches (20 cm) from the ceiling. Then, you can inject slow-rising cavity-fill foam insulation into these holes. All that’s left after you’re done injecting insulation is to patch the drywall holes and paint.

How to insulate walls without removing the drywall

Can You Fill Your Walls With Expanding Foam Insulation?

Cavity-fill foam insulation allows you to insulate walls without removing drywall. You can hire a contractor to inject foam insulation into wall cavities without removing drywall, or you can do the job yourself. 

  • Expanding foam insulation is an increasingly popular, energy-efficient insulation choice.
  • Several contractors specialize in injecting foam insulation into walls without removing drywall.
  • If you want to tackle the job yourself, our article will teach you how to install foam insulation without removing your drywall.

If you have experience using a stud finder, electric drill, and other standard home improvement tools, you’ll be able to perform the necessary steps for this job. You can purchase this injectable foam insulation kit and get started today.

Is Cavity-Fill Foam Insulation Good?

Closed cell spray foam insulation is among the best types of insulation. Insulation is ranked based on its R-value, which measures how well it can retain heated or cooled air. The higher the R-value, the better the insulation is. Closed cell, cavity-fill foam insulation has an R-value ranging from 5.9 to 7 per inch. In comparison, traditional fiberglass batt insulation has an R-value of 3.1 to 3.4. This makes sprayable foam insulation a far better choice than most traditional insulations.

  • Insulation effectiveness is measured by the R-Value. 
  • The higher the R-value, the more effective a particular type of insulation is.
  • Foam insulation that can be sprayed without removing drywall has an R-Value of 5.9–7.0.
  • Rolls and batts of fiberglass insulation have an R-Value of 3.1–3.4.
  • Choosing cavity-fill insulation over other types can lower your energy bills.

Due to its extremely high R-value, expanding foam insulation is a great choice for homeowners. Not only can you insulate walls without removing your drywall, but you’ll also get higher-quality insulation. This means your home will lock in more warm air during winter and trap cool air during the hot summer months.

7 Steps to Insulate Walls Without Tearing Out Drywall

Whether you want to insulate your walls with cavity-fill insulation to reduce energy costs or you just want to insulate a room without stripping the drywall off your walls, you can do the job yourself. Below are the steps to make sure the job is done right.

Locate Your Wall Studs

Before you can begin drilling holes and injecting spray foam insulation materials, first you need to find the location of the studs in your walls. In later steps, you will have to drill holes between each pair of studs so that you can fill each section of your wall with insulation. To get started:

  • Use this stud finder to locate wall studs that run from the floor to the ceiling.
  • Mark the path of each wall stud with a pencil or chalk.
  • Wall studs are 16–24 inches apart in most homes.
  • Check for horizontal “fire breaks” that run between wall studs.
  • Mark the location of all horizontal fire breaks—you will have to inject insulation above and below these barriers.

Many newer homes have horizontal 2x4s spanning between the wall studs. These are fire breaks that increase the safety of your home. However, foam insulation can’t pass through fire breaks. So, it’s important to scan your walls for horizontal studs spanning the vertical studs. If you find these, mark them clearly with a pencil.

Find Wires and Plumbing

Once you’ve located the wooden studs in your wall, it’s time to find any plumbing lines and live electrical wires. The stud finder we suggested above has a scanning mode that detects live electrical wires. It’s essential to find and mark electrical wiring paths with wire. That way, you can avoid drilling into wires, which could be hazardous.

  • Use a stud finder with the ability to detect live electrical wires.
  • Find and mark the paths of any wires in the walls you wish to insulate—this will prevent you from drilling into live wires.
  • Scan the wall to find plumbing lines so you can avoid drilling into a water-filled pipe in later steps.
  • Even if you have plastic water pipes, you can use our specialized guide to find these plumbing lines.

If you are planning to insulate a finished wall in a bathroom, kitchen, laundry room, or in a room below an upstairs bathroom, there may be pipes running through the walls. Follow our tips for using a stud finder to locate pipes, then mark the path of any plumbing lines. This will prevent you from drilling into your plumbing, which will save you from a broken plumbing line gushing water inside your walls.

Drill Holes

Once you’ve marked the location of studs, wires, and plumbing lines, you’re ready to drill the holes necessary for injecting foam insulation into your walls. Equip your drill with a 3-inch diameter (75 mm) drill bit. Drill one hole between each wall stud. The hole should be made 8 inches (20 cm) below the ceiling.

  • Equip an electric drill with this 3-inch drill bit.
  • Drill one hole centered between each set of wall studs.
  • The hole should be drilled 8 inches (20 cm) below the ceiling.
  • If your wall has horizontal fire breaks, drill additional holes 8 inches below each fire break.
  • Make sure to avoid drilling into electrical wiring and plumbing as you work.

If your walls have horizontal fire breaks spanning between the studs, you will need to drill multiple holes—one 8 inches below the ceiling, followed by additional holes 8 inches below each fire break. This will allow you to fill each part of your wall with foam insulation. This prevents air leaks and ensures energy efficiency for both interior and exterior walls.

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Take Safety Measures

Before you begin insulating your walls it is essential to read the operating and safety instructions for your insulation kit. Some precautions you should take include:

  • Wear long sleeves, pants, work boots, goggles, nitrile gloves, and breath protection, such as this mask.
  • Ventilate the room by opening windows.
  • Turn off all HVAC or other in-home ventilation systems—if left on they can spread chemical fumes through your home.
  • Keep pets and family members out of the working area.
  • Do not smoke or allow any open flames in the working area.

In addition to these guidelines, follow all specific safety guidelines for your insulation product of choice. It’s also essential to read the product manual and follow all guidelines for safe operation.

Spray Foam Insulation into the Walls

Begin by inserting the nozzle of the foam sprayer into the first hole drilled in your drywall. Angle the nozzle downward. It is a good idea to partially block the hole around the sprayer with a cloth to prevent foam from spraying out of the hole. Once you’re ready, pull the trigger on the nozzle to begin feeding insulation foam into your wall.

  • Insert the sprayer nozzle into one of the holes drilled in your wall.
  • Angle the nozzle downward.
  • With your free hand, press a cloth around the nozzle to prevent foam from spraying back into the room.
  • Pull the trigger on the sprayer to begin filling the space between the wall studs with foam.
  • Once you feel resistance as the wall cavity fills with foam, remove the nozzle and move to the next hole.

Continue spraying insulation into the wall until you feel resistance as the foam expands inside the wall and fills the cavity between the studs. Then, remove the nozzle, move to the next hole, and repeat. The foam will expand within minutes to fill the space, but it will require 1 hour to harden.

Patch Holes in Drywall

Once your foam insulation has hardened, you can begin patching the holes you drilled in your drywall. In order to make patching easier, use drywall repair mesh. Alternatively, you can purchase a drywall repair kit designed specifically for fixing holes 3–5 inches (7.5–13 cm) in diameter.

  • Wait at least 1 hour for the insulation foam to fully dry.
  • Patch the holes drilled in your drywall by using this drywall repair kit.
  • Apply joint compound over the repair fabric to make a smooth finish.
  • Allow the joint compound to dry for 24 hours before sanding and applying additional coats of joint compound.

If you do not use a drywall repair kit, make sure to patch the wall using drywall mesh tape and joint compound. If you try to patch the 3-inch-diameter hole with joint compound alone, the results will not be attractive or long-lasting.

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Repaint the Interior Walls

Once you have patched the holes in your drywall, follow our complete guide to hiding drywall patch marks. Getting a perfect finished look will require multiple coats of joint compound before repainting the wall.

  • Smooth out drywall patches with additional coats of joint compound and finishing compound.
  • Repaint the entire wall where drywall patches were made to make them completely invisible.
  • The end result will be a high-quality job without the labor of ripping out your drywall.

Drilling holes in drywall, filling wall cavities with foam insulation, and patching the drywall holes is fast, less messy than tearing out your drywall, and results in a very energy-efficient home. With the reduced heat transfer caused by your new insulation, your utility bills will typically be much lower.

Can You Insulate Walls Without Removing Drywall?

In order to insulate closed walls without tearing off a single drywall panel, follow these steps:

  • Use a stud finder to locate all studs and fire breaks in your wall—mark their location with a pencil or chalk.
  • Switch your stud finder to different scanning modes to locate and mark the path of electrical wires and plumbing lines.
  • Drill 3-inch diameter holes between wall studs so you can spray insulation into the walls, making sure to avoid wires and plumbing lines.
  • Don proper PPE, ventilate the room, and review the instructions for your insulation kit.
  • Insert the foam sprayer nozzle into each hole, angle it downward, and spray to fill the area between the wall studs.
  • Use a drywall repair kit and joint compound to patch the holes drilled in your wall.
  • Sand and finish your drywall patches before repainting the wall.

By following these steps you will be able to safely insulate your own home with an extremely energy-efficient foam insulation. Plus, our guides to patching and painting drywall will ensure that the finished product looks as good as new.

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